Bump spotless-maven-plugin from 2.7.0 to 2.8.1

Bumps [spotless-maven-plugin](https://github.com/diffplug/project) from 2.7.0 to 2.8.1.
- [Release notes](https://github.com/diffplug/project/releases)
- [Commits](https://github.com/diffplug/project/commits)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pom.xml

@@ -434,7 +434,7 @@
       <plugin>
         <groupId>com.diffplug.spotless</groupId>
         <artifactId>spotless-maven-plugin</artifactId>
-        <version>2.7.0</version>
+        <version>2.8.1</version>
         <configuration>
           <formats>
             <!-- common settings -->